Isoflurane Anesthesia Research Articles

An anesthetic protocol for preserving functional network structure in the marmoset monkey brain

Abstract Initiatives towards acquiring large-scale neuroimaging data in non-human primates promise improving translational neuroscience and cross-species comparisons. Crucial among these efforts is the need to expand sample sizes while reducing the impact of anesthesia on the functional properties of brain networks. Yet, the effects of anesthesia on non-human primate brain networks remain unclear. Here, we demonstrate using functional magnetic resonance imaging (fMRI) at 9.4 tesla that isoflurane anesthesia induces a variety of brain states in the marmoset brain with dramatically altered functional connectivity profiles. As an alternative, we recommend using a continuous infusion of the sedative medetomidine, supplemented with a low concentration of isoflurane. Using this protocol in eight marmosets, we observed robust visual activation during flickering light stimulation and identified resting-state networks similar to the awake state. In contrast, isoflurane alone led to a suppressed visual activation and the absence of awake-like network patterns. Comparing states using a graph-theoretical approach, we confirmed that the structure of functional networks is preserved under our proposed anesthesia protocol but is lost using isoflurane alone at concentration levels greater than 1%. We believe that the widespread adoption of this protocol will be a step towards advancing translational neuroscience initiatives in non-human primate neuroimaging. To promote the collaborative use of neuroimaging resources, we openly share our datasets (https://zenodo.org/records/11118775).

LanCL1 protects developing neurons from long-term isoflurane anesthesia-induced neurotoxicity

Research has revealed that prolonged or repeated exposure to isoflurane, a common general anesthetic, can lead to cognitive and behavioral deficiencies, particularly in early life. The brain contains a wealth of LanCL1, an antioxidant enzyme that is thought to mitigate oxidative stress. Nevertheless, its precise function in mammals remains uncertain. This study uncovered a decrease in the expression of LanCL1 due to prolonged isoflurane anesthesia, accompanied by anesthesia-induced neurotoxicity in vivo and in vitro. To better understand LanCL1's essential function, LanCL1 overexpressing adenoviruses were employed to increase LanCL1 levels. The outcomes were analyzed using western blot and immunofluorescence methods. According to the findings, extended exposure to isoflurane anesthesia may lead to developmental neurotoxicity in vivo and in vitro. The anesthesia-induced neurotoxicity was concomitant with a reduction in LanCL1 expression. Moreover, the study revealed that overexpression of LanCL1 can mitigate the neurotoxic effects of isoflurane anesthesia, resulting in improved synaptic growth, less reactive oxygen species, enhanced cell viability and rescued memory deficits in the developing brain. In conclusion, prolonged anesthesia-induced LanCL1 deficiency could be responsible for neurotoxicity and subsequent cognitive impairments in the developing brain. Additional LanCL1 counteracts this neurotoxic effect and protects neurons from long-term isoflurane anesthesia.

Effect of Atracurium and Rocuronium on the State and Response Entropy during Isoflurane Anesthesia: Randomized Prospective Study

Abstract Background Several researches have inspected the impact of inhalation anesthetics, intravenous anesthetics, and muscle relaxants on spectral entropy, but many didn’t evaluate the extent of neuromuscular block. Besides, they didn’t inspect the impact of distinct degrees of neuromuscular blockade on spectral entropy under dissimilar saturations of isoflurane inhalation. Hence, this study evaluated variant degrees of minimum alveolar concentration (MAC) to estimate the isoflurane concentration, along with various level of neuromuscular blockade. Aim of this study is to evaluate the effect of muscle relaxants (atracurium and rocuronium) on entropy readings (state, response entropy and response- state difference) during isoflurane anesthesia. This is a prospective randomized study where forty patients were included and divided into two study groups; patients in Group A received atracurium, while patients in Group R received rocuronium. State and response entropy were observed under MAC 0.8% and 1% under 50% and 100% neuromuscular blockage. Results There was a positive correlation between state (SE) and response entropy (RE) at baseline, different MAC, and different train of four (TOF) for both atracurium and rocuronium. State and response entropy decreased with increasing MAC of isoflurane (p < 0.001), while atracurium and rocuronium at TOF 50% and 100% showed no effect on SE or RE or RE-SE (P > 0.05). Conclusions State and response entropy can be used effectively to evaluate depth of anesthesia at different isoflurane MAC and atracurium or rocuronium doses. Registration number: ClinicalTrials.gov Identifier: NCT 05097508, Registered 5 October 2021 - prospectively registered, http://www.ClinicalTrial.gov

Common functional mechanisms underlying dynamic brain network changes across five general anesthetics: A rat fMRI study.

Reversible loss of consciousness is the primary therapeutic endpoint of general anesthesia; however, the drug-invariant mechanisms underlying anesthetic-induced unconsciousness are still unclear. This study aimed to investigate the static, dynamic, topological and organizational changes in functional brain network induced by five clinically-used general anesthetics in the rat brain. Male Sprague-Dawley rats (n = 57) were randomly allocated to received propofol, isoflurane, ketamine, dexmedetomidine, or combined isoflurane plus dexmedetomidine anesthesia. Resting-state functional magnetic resonance images were acquired under general anesthesia and analyzed for changes in dynamic functional brain networks compared to the awake state. Different general anesthetics induced distinct patterns of functional connectivity inhibition within brain-wide networks, resulting in multi-level network reorganization primarily by impairing the functional connectivity of cortico-subcortical networks as well as by reducing information transmission capacity, intrinsic connectivity, and network architecture stability of subcortical regions. Conversely, functional connectivity and topological properties were preserved within cortico-cortical networks, albeit with fewer dynamic fluctuations under general anesthesia. Our findings highlighted the effects of different general anesthetics on functional brain network reorganization, which might shed light on the drug-invariant mechanism of anesthetic-induced unconsciousness.

Isoflurane increases the activity of the vascular matrix metalloproteinase-2 in non-pregnant rats and increases the nitric oxide metabolites in pregnancy.

Surgeries that require general anesthesia occur in 1.5-2% of gestations. Isoflurane is frequently used because of its lower possibility of affecting fetal growth. Therefore, we examined the isoflurane anesthesia-induced effects on maternal hemodynamic and vascular changes. We hypothesized that isoflurane would enhance endothelium-dependent vasodilation as a consequence of increased nitric oxide and decreased metalloproteinases (MMPs). Female rats (n=28) were randomized into 4 groups (7 rats/group): conscious (non-anesthetized) non-pregnant group, non-pregnant anesthetized group, conscious pregnant group, and pregnant anesthetized group. Anesthesia was performed on the 20th pregnancy day, and hemodynamic parameters were monitored. Nitric oxide metabolites, gelatinolytic activity of MMP-2 and MMP-9, and the vascular function were assessed. Isoflurane caused no significant hemodynamic changes in pregnant compared with non-pregnant anesthetized group. Impaired acetylcholine-induced relaxations were observed only in conscious non-pregnant group (by approximately 62%) versus 81% for other groups. Phenylephrine-induced contractions were greater in endothelium-removed aorta segments of both pregnant groups (with or without isoflurane) compared with non-pregnant groups. Higher nitric oxide metabolites were observed in anesthetized pregnant in comparison with the other groups. Reductions in the 75 kDa activity and concomitant increases in 64 kDa MMP-2 isoforms were observed in aortas of pregnant anesthetized (or not) groups compared with conscious non-pregnant group. Isoflurane anesthesia shows stable effects on hemodynamic parameters and normal MMP-2 activation in pregnancy. Furthermore, there were increases in nitric oxide bioavailability, suggesting that isoflurane provides protective actions to the endothelium in pregnancy.

Isoflurane anesthesia and sleep deprivation trigger delayed and selective sleep alterations

Isoflurane anesthesia (IA) partially compensates NREM sleep (NREMS) and not REM sleep (REMS) requirement, eliciting post-anesthetic REMS rebound. Sleep deprivation triggers compensatory NREMS rebounds and REMS rebounds during recovery sleep as a result of the body’s homeostatic mechanisms. A combination of sleep deprivation and isoflurane anesthesia is common in clinical settings, especially prior to surgeries. This study investigates the effects of pre-anesthetic sleep deprivation on post-anesthetic sleep–wake architecture. The effects of isoflurane exposure (90 min) alone were compared with the effects of isoflurane exposure preceded by experimental sleep deprivation (6 h, gentle handling) on recovery sleep in adult mice by studying the architecture of post-anesthetic sleep for 3 consecutive post-anesthetic days. Effects of isoflurane anesthesia on recovery sleep developed only during the first dark period after anesthesia, the active phase in mice. During this time, mice irrespective of preceding sleep pressure, showed NREMS and REMS rebound and decreased wakefulness during recovery sleep. Additionally, sleep deprivation prior to isoflurane treatment caused a persistent reduction of theta power during post-anesthetic REMS at least for 3 post-anesthetic days. We showed that isoflurane causes NREMS rebound during recovery sleep which suggests that isoflurane may not fully compensate for natural NREMS. The study also reveals that isoflurane exposure preceded by sleep deprivation caused a persistent disruption of REMS quality. We suggest that preoperative sleep deprivation may impair postoperative recovery through lasting disruption in sleep quality.

Comparison of cardiopulmonary effects of propofol, ketamine–propofol and isoflurane anesthesia in the domestic chicken (Gallus gallus domesticus)

ObjectiveTo compare the effects of propofol, ketamine–propofol and isoflurane, at similar anesthetic depth, on cardiopulmonary variables in unpremedictated chickens. Study designProspective, randomized, crossover experimental trial. AnimalsA total of 10 male Leghorn domestic chickens, aged 3 months and body mass 1.4–2.0 kg. MethodsBirds were randomly assigned to each of three anesthetic protocols, 7 days apart: intravenous propofol, intravenous ketamine–propofol or isoflurane. Anesthesia was induced (indicated by loss of righting reflex and tracheal intubation) and maintained with propofol (10 mg kg–1 minute–1, then 1.1 mg kg–1 minute–1), ketamine–propofol (5 mg mL–1 ketamine and 5 mg mL–1 propofol combined; 10 mg kg–1 minute–1, then 1.1 mg kg–1 minute–1) or isoflurane [5% vaporizer setting initially, then end-tidal concentration (Fe′Iso) of 2%] for 65 minutes. Anesthesia was maintained at a similar anesthetic depth based upon positive or negative responses to toe pinch. Heart rate (HR), respiratory rate (fR), noninvasive arterial blood pressure and arterial blood gases were measured during anesthesia. Propofol or ketamine–propofol infusion rates and Fe′Iso required to prevent movement in response to a noxious stimulus and recovery times were recorded. ResultsAnesthesia induction dose was 9.0 ± 0.8 (mean ± SD) and 12.2 ± 0.3 mg kg–1 for propofol and ketamine–propofol, respectively. Propofol and ketamine–propofol infusion rates and Fe′Iso required to prevent movement in response to the noxious stimulus were 0.88 ± 0.14 mg kg–1 minute–1, 0.92 ± 0.14 mg kg–1 minute–1 and 1.45 ± 0.28%, respectively. Cardiopulmonary variables remained clinically acceptable, but ketamine–propofol was associated with a significantly higher HR (p = 0.0001) and lower fR (p = 0.0001). Time to extubation did not differ among treatments. Conclusions and clinical relevanceCardiovascular and respiratory variables were maintained within normal ranges in all treatments. Coadministration of ketamine with propofol significantly reduced the induction and maintenance dose of propofol.

Effect of reducing isoflurane level on glucosamine uptake in the mouse brain during magnetic resonance imaging studies

Anesthesia is often required during magnetic resonance imaging (MRI) examinations in animal studies. Anesthetic drugs differ in their capacity to interfere with homeostatic mechanisms responsible for glucose metabolism in the brain, which may create a constraint in the study design. Recent studies suggest that the chemical exchange saturation transfer (CEST) MRI scanning technique can detect localized metabolic changes in rodent brains induced by the uptake of glucose or its analogs; however, most of these studies do not account for the impact of anesthesia type on the brain metabolism. Herein, we aimed to evaluate the effect of reduced isoflurane levels on the preclinical imaging of glucosamine (GlcN) uptake in healthy mouse brains to establish optimal conditions for future brain imaging studies using the CEST MRI technique. The commonly used anesthesia protocol for longitudinal MRI examinations using 1.5% isoflurane level was compared to that using a mixture of low isoflurane (0.8%) level combined with midazolam (2 mg/kg, SC). Magnetization transfer ratio asymmetry (MTRasym) and area under the curve (AUC) analyses were used to characterize GlcN signals in the brain. The results indicated that mice injected with GlcN and anesthetized with 1.5% isoflurane exhibited low and insignificant changes in the MTRasym and AUC signals in the frontal cortex, whereas mice administered with 0.8% isoflurane combined with midazolam demonstrated a significant increase in these signals in the frontal cortex. This study highlights the diverse GlcN metabolic changes observed in mouse brains under variable levels of isoflurane anesthesia using the CEST MRI method. The results suggest that it is feasible to maintain anesthesia with low-dose isoflurane by integrating midazolam, which may enable the investigation of GlcN uptake in the brain. Thus, reducing isoflurane levels may support studies into mouse brain metabolism using the CEST MRI method and should be considered in future studies.

Identification of hypothermia-inducing neurons in the preoptic area and activation of them by isoflurane anesthesia and central injection of adenosine

Hibernation and torpor are not passive responses caused by external temperature drops and fasting but are active brain functions that lower body temperature. A population of neurons in the preoptic area was recently identified as such active torpor-regulating neurons. We hypothesized that the other hypothermia-inducing maneuvers would also activate these neurons. To test our hypothesis, we first refined the previous observations, examined the brain regions explicitly activated during the falling phase of body temperature using c-Fos expression, and confirmed the preoptic area. Next, we observed long-lasting hypothermia by reactivating torpor-tagged Gq-expressing neurons using the activity tagging and DREADD systems. Finally, we found that about 40–60% of torpor-tagged neurons were activated by succeeding isoflurane anesthesia and by icv administration of an adenosine A1 agonist. Isoflurane-induced and central adenosine-induced hypothermia is, at least in part, an active process mediated by the torpor-regulating neurons in the preoptic area.Graphical abstract

Isoflurane-induced neuroinflammation and NKCC1/KCC2 dysregulation result in long-term cognitive disorder in neonatal mice

BackgroundThe inhalational anesthetic isoflurane is commonly utilized in clinical practice, particularly in the field of pediatric anesthesia. Research has demonstrated its capacity to induce neuroinflammation and long-term behavioral disorders; however, the underlying mechanism remains unclear [1]. The cation-chloride cotransporters Na+–K+–2Cl−–1 (NKCC1) and K+–2Cl−–2 (KCC2) play a pivotal role in regulating neuronal responses to gamma-aminobutyric acid (GABA) [2]. Imbalances in NKCC1/KCC2 can disrupt GABA neurotransmission, potentially leading to neural circuit hyperexcitability and reduced inhibition following neonatal exposure to anesthesia [3]. Therefore, this study postulates that anesthetics have the potential to dysregulate NKCC1 and/or KCC2 during brain development.MethodsWe administered 1.5% isoflurane anesthesia to neonatal rats for a duration of 4 h at postnatal day 7 (PND7). Anxiety levels were assessed using the open field test at PND28, while cognitive function was evaluated using the Morris water maze test between PND31 and PND34. Protein levels of NKCC1, KCC2, BDNF, and phosphorylated ERK (P-ERK) in the hippocampus were measured through Western blotting analysis. Pro-inflammatory cytokines IL-1β, IL-6, and TNF-α were quantified using ELISA.ResultsWe observed a decrease in locomotion trajectories within the central region and a significantly shorter total distance in the ISO group compared to CON pups, indicating that isoflurane induces anxiety-like behavior. In the Morris water maze (MWM) test, rats exposed to isoflurane exhibited prolonged escape latency onto the platform. Additionally, isoflurane administration resulted in reduced time spent crossing in the MWM experiment at PND34, suggesting long-term impairment of memory function. Furthermore, we found that isoflurane triggered activation of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α; downregulated KCC2/BDNF/P-ERK expression; and increased the NKCC1/KCC2 ratio in the hippocampus of PND7 rats. Bumetadine (NKCC1 specific inhibitors) reversed cognitive damage and effective disorder induced by isoflurane in neonatal rats by inhibiting TNF-α activation, normalizing IL-6 and IL-1β levels, restoring KCC2 expression levels as well as BDNF and ERK signaling pathways. Based on these findings, it can be speculated that BDNF, P-ERK, IL-1β, IL-6 and TNF - α may act downstream of the NKCC1/KCC2 pathway.ConclusionsOur findings provide evidence that isoflurane administration in neonatal rats leads to persistent cognitive deficits through dysregulation of the Cation-Chloride Cotransporters NKCC1 and KCC2, BDNF, p-ERK proteins, as well as neuroinflammatory processes.

GABAergic neurons of anterior thalamic reticular nucleus regulate states of consciousness in propofol- and isoflurane-mediated general anesthesia.

The thalamus system plays critical roles in the regulation of reversible unconsciousness induced by general anesthetics, especially the arousal stage of general anesthesia (GA). But the function of thalamus in GA-induced loss of consciousness (LOC) is little known. The thalamic reticular nucleus (TRN) is the only GABAergic neurons-composed nucleus in the thalamus, which is composed of parvalbumin (PV) and somatostatin (SST)-expressing GABAergic neurons. The anterior sector of TRN (aTRN) is indicated to participate in the induction of anesthesia, but the roles remain unclear. This study aimed to reveal the role of the aTRN in propofol and isoflurane anesthesia. We first set up c-Fos straining to monitor the activity variation of aTRNPV and aTRNSST neurons during propofol and isoflurane anesthesia. Subsequently, optogenetic tools were utilized to activate aTRNPV and aTRNSST neurons to elucidate the roles of aTRNPV and aTRNSST neurons in propofol and isoflurane anesthesia. Electroencephalogram (EEG) recordings and behavioral tests were recorded and analyzed. Lastly, chemogenetic activation of the aTRNPV neurons was applied to confirm the function of the aTRN neurons in propofol and isoflurane anesthesia. c-Fos straining showed that both aTRNPV and aTRNSST neurons are activated during the LOC period of propofol and isoflurane anesthesia. Optogenetic activation of aTRNPV and aTRNSST neurons promoted isoflurane induction and delayed the recovery of consciousness (ROC) after propofol and isoflurane anesthesia, meanwhile chemogenetic activation of the aTRNPV neurons displayed the similar effects. Moreover, optogenetic and chemogenetic activation of the aTRN neurons resulted in the accumulated burst suppression ratio (BSR) during propofol and isoflurane GA, although they represented different effects on the power distribution of EEG frequency. Our findings reveal that the aTRN GABAergic neurons play a critical role in promoting the induction of propofol- and isoflurane-mediated GA.

Dexmedetomidine Inhibits Hippocampal Neuronal Damage Caused by Persistent Isoflurane-Induced Hypotension in Rat Model of Chronic Cerebral Hypoperfusion.

Purpose The purpose of this study was to investigate the effect of dexmedetomidine (DEX) on hypotension-induced neuronal damage in a chronic cerebral hypoperfusion (CCH) model of rats, an established model of cerebral white matter lesions (WML) in humans, which is prevalent in the elderly and closely related to cognitive decline. Methods The CCH model rats were randomly assigned to one of four groups: normotension + no DEX (NN) group (n = 6), normotension + DEX (ND) group (n = 6), hypotension + no DEX (HN) group (n = 6), or hypotension + DEX (HD) group (n = 6). Under isoflurane anesthesia, mean arterial blood pressure was maintained at or above 80 mmHg (normotension) or below 60 mmHg (hypotension) for a duration of two hours. The DEX groups received 50 μg of DEX intraperitoneally. Two weeks later, the Y-maze test and, after preparing brain slices, immunohistochemical staining were performed using antibodies against neuronal nuclei (NeuN), microtubule-associated protein 2 (MAP2), glial fibrillary acidic protein (GFAP), and Ionized calcium-binding adapter molecule 1 (Iba1). Results Behavioral observations showed no significant differences among the groups. Significant reductions of both NeuN-positive cells and the MAP2-positive area were found in the hippocampal CA1 in the HN group compared with NN and ND groups, but not in the HD group. GFAP and Iba-1-positive areas were significantly increased in the HN group, but not in the HD group. Conclusion DEX significantly ameliorated hypotension-induced neuronal damage and both astroglial and microglial activation in the CA1 region of CCH rats.

Intravesical local administration of pembrolizumab for treatment of bladder cancer: A novel strategy to minimize toxicity.

e14687 Background: A major hallmark of bladder cancer (BCa) is a higher treatment success rate than prostate cancer following stimulation of innate anti-tumor immune response either by intravesical BCG or to FDA approved intravenous anti-PD1 checkpoint antibody (pembrolizumab) approved for BCG resistant BCa since 2021. However, injected pembrolizumab is characterized by a markedly higher incidence (66%) of serious adverse events than the median duration of complete response of ~40% for non-muscle invasive BCa (NMIBC) and 15-20% for invasive BCa. Since the toxicity (fatigue, Pneumonitis and diarrhea) of injected pembrolizumab is linked to systemic breakdown of T-cell mediated immune surveillance we enquired whether analogous to BCG, pembrolizumab can be administered intravesically to safely induce a localized anti-tumor response in mouse model of BCa. Methods: Six weeks old female mice of B6D2F1 strain (n=10) were ad libitum fed carcinogen, N-butyl-N-4-hydroxybutyl nitrosamine (BBN) in drinking water (0.05% w/v) for 12 weeks. The presence of BBN evoked tumor was ascertained by unenhanced T2 weighted MRI at week 11 prior to single intravesical dosing by 24G transurethral catheter under isoflurane anesthesia of 0.1mL vehicle (sterile water) with or without 0.3mg of Pembrolizumab (Lipella Pharmaceuticals). 6 weeks later, T2 weighted MRI was repeated together with T1 mapping by ICE-MRI prior to organ harvest. Results: BBN feeding evoked multiclonal tumors (red*) of comparable size on T2 weighted MRI at week 11 but repeat MRI 7 weeks after treatment revealed that tumor progression and perivesical invasion noted in vehicle group was arrested in pembrolizumab group. Longest dimension of BBN tumor in vehicle treated mice was ≥ 1mm longer (p<0.05) than in pembrolizumab treated mice. T1 mapping revealed thickened bladder wall missed by T2 MRI. Conclusions: These findings on single intravesical dose of pembrolizumab (10mg/kg) in mice are consistent with human study on multiple intravesical dosing of BCG plus pembrolizumab (1-2mg/kg) in BCG resistant NMIBC patients. Intravesical pembrolizumab mirrors the limited systemic uptake of radiolabelled antibodies together with substantially higher ingress into tumor foci. The tumor selective ingress for BCa immunotherapy without any toxicity will be enhanced with Lipella Pharmaceutical’s liposomal delivery of Pembrolizumab.

Fer-1 Protects against Isoflurane-Induced Ferroptosis in Astrocytes and Cognitive Impairment in Neonatal Mice.

Early and prolonged exposure to anesthetic agents could cause neurodevelopmental disorders in children. Astrocytes, heavily outnumber neurons in the brain, are crucial regulators of synaptic formation and function during development. However, how general anesthetics act on astrocytes and the impact on cognition are still unclear. In this study, we investigated the role of ferroptosis and GPX4, a major hydroperoxide scavenger playing a pivotal role in suppressing the process of ferroptosis, and their underlying mechanism in isoflurane-induced cytotoxicity in astrocytes and cognitive impairment. Our results showed that early 6h isoflurane anesthesia induced cognitive impairment in mice. Ferroptosis-relative genes and metabolic changes were involved in the pathological process of isoflurane-induced cytotoxicity in astrocytes. The level of GPX4 was decreased while the expression of 4-HNE and generation of ROS were elevated after isoflurane exposure. Selectively blocking ferroptosis with Fer-1 attenuated the abovementioned cytotoxicity in astrocytes, paralleling with the reverse of the changes in GPX4, ROS and 4-HNE secondary to isoflurane anesthesia. Fer-1 attenuated the cognitive impairment induced by prolonged isoflurane exposure. Thus, ferroptosis conduced towards isoflurane-induced cytotoxicity in astrocytes via suppressing GPX4 and promoting lipid peroxidation. Fer-1 was expected to be an underlying intervention for the neurotoxicity induced by isoflurane in the developing brain, and to alleviate cognitive impairment in neonates.

#2359 Kinetic modifications in cardiac remodeling in a rat model of CKD

Abstract Background and Aims The bi-directional relationship between the kidneys and heart leads to different forms of cardiorenal syndrome (CRS) in which acute or chronic dysfunction in one organ affects the other. CRS type 4 is characterized by chronic kidney disease leading to the impairment of cardiac function through diastolic dysfunction and cardiac remodeling, such as fibrosis and hypertrophy. The progression of CRS type 4 occurs dynamically thus identifying key changes could prove beneficial for treatment and prediction of outcome for the patients. This present study assessed the impact on heart remodeling and function after 12 and 24 weeks of chronic kidney disease in rats undergoing subtotal nephrectomy. Method Twelve-week-old Sprague Dawley male rats either underwent 5/6 nephrectomy (SNX) or Sham operated and were sacrificed at 12 or 24 weeks after kidney infarction. Serum creatine levels were assessed using the epoc® Blood Analysis System. Before sacrifice, a catheter was inserted into the right carotid artery for systolic arterial pressure (SAP) measurement. Echocardiography (VisualSonics/Fujifilm) was performed under isoflurane anesthesia. To determine the diastolic function of the heart, mitral flow was assessed and recorded using a pulse-wave doppler. The peak early filling (E wave)-to-late diastolic filling (A wave) ratio (E/A) as well as E deceleration time was used to determine diastolic function. Left Ventricle posterior wall thickness (LVPW_S) was measured during end-systole and end-diastole. Image analyses were performed using VisualSonics Vevolab 3.1.0 software. Fibrosis of the kidney and left ventricle was determined through Sirius Red histology staining. The mRNA expression levels of FGF23 and GDF-15 were measured through qPCR. Unpaired T-test, Non-parametric, or One-way ANOVA were applied, and log transformation was performed when applicable. Statistical Analysis was performed using GraphPad Prism 8 software. Results The plasma creatinine dosage confirmed the renal insufficiency of the animals however, no changes were observed between 12 and 24 weeks of SNX (Table 1). Fibrosis in the kidney increased between 12 and 24 weeks of SNX as well as between their corresponding Sham (Table 1). Twenty-four weeks of SNX rats exhibited increased heart fibrosis in comparison to sham (Table 1). An increase in SAP was observed at 24 weeks of SNX in comparison to their Sham (Table 1). Cardiac remodeling between 12 and 24 weeks of SNX was observed through the increase in the left ventricle wall thickness (Table 1) (Fig. 1A). This was coupled with an increase in the expression of cardiac remodeling and protective-related genes FGF23 and GDF-15 (Fig. 1B,C). Diastolic function, as measured by E/A, remained unchanged in the model at both ages (Table 1). E deceleration time decreased at 24 weeks of SNX compared to their Sham (Table 1). Conclusion These preliminary results show a change in cardiac remodeling and function at 24 weeks of SNX compared to Sham. Between 12 and 24 weeks of SNX, changes in cardiac remodeling, namely hypertrophy of the posterior wall, can be observed. These changes were accompanied by an increase in FGF23 and GDF-15. As our model of cardio-renal syndrome has been characterized; we will turn our attention to the signaling involved in the establishment of cardiac fibrosis. This pre-clinical model will also make it possible to test new anti-fibrosis treatments.

Clinical and Hematological Effect of Constant Rate Infusion of Ketamine Alone and Ketamine-dexmedetomidine Combination on Isoflurane Anesthesia in Horses

Background: Anaesthetic management of horses for a successful surgery is of utmost importance but a risky procedure than other companion animals. Peri-aneasthetic morbidity and mortality in horses could be alarming if proper combinations of drugs were not used. Balanced anaesthetic combinations are being explored by various authors to find safer combinations.Therefore current study was planned to evaluate the effect of CRI of ketamine alone and ketamine-dexmedetomidine combination for isoflurane anesthesia in horses. Methods: Twenty four clinical cases of horses were randomly divided into three groups S, D and DK, having eight animals in each. Xylazine (1 mg/kg) and butorphanol (0.05 mg/kg) were given intravenously for premedication and ketamine (2 mg/kg) and midazolam (0.2 mg/kg) were used for induction of anesthesia. Normal saline (1000 ml/hour), ketamine alone (2 mg/kg/hr), ketamine (2 mg/kg/hr) and dexmedetomidine (2 µg/kg/hr) combination were given as CRI in groups S, K and KD, respectively. Thiopentone sodium (200 mg bolus, 5%) was given as fast intravenous to facilitate endotracheal intubation in some of the cases. Anesthesia was maintained with isoflurane in oxygen and anesthetic efficacy was evaluated based on clinical and haematological parameters. Result: Overall quality of sedation, muscle relaxation, response to surgical stimuli, quality of intubation, anesthetic depth and quality of recovery was significantly (p less than 0.05) better in group KD. Down-time (min) and duration of anesthesia were non significantly less in group KD. CRI of ketamine and dexmedetomidine combination was having significant (p less than 0.05) thiopentone sodium and isoflurane sparing effect. Heart rateand RR, did not show any significant variation among groups but rectal temperature was significantly low in KD group than groups S and K. CRI of ketamine-Dexmedetomidine combination produced a better quality of anesthesia and significant thiopentone sodium and isoflurane sparing effect thus was found suitable for anesthesia of horses.

Synapse-Specific Trapping of SNARE Machinery Proteins in the Anesthetized Drosophila Brain.

General anesthetics disrupt brain network dynamics through multiple pathways, in part through postsynaptic potentiation of inhibitory ion channels as well as presynaptic inhibition of neuroexocytosis. Common clinical general anesthetic drugs, such as propofol and isoflurane, have been shown to interact and interfere with core components of the exocytic release machinery to cause impaired neurotransmitter release. Recent studies however suggest that these drugs do not affect all synapse subtypes equally. We investigated the role of the presynaptic release machinery in multiple neurotransmitter systems under isoflurane general anesthesia in the adult female Drosophila brain using live-cell super-resolution microscopy and optogenetic readouts of exocytosis and neural excitability. We activated neurotransmitter-specific mushroom body output neurons and imaged presynaptic function under isoflurane anesthesia. We found that isoflurane impaired synaptic release and presynaptic protein dynamics in excitatory cholinergic synapses. In contrast, isoflurane had little to no effect on inhibitory GABAergic or glutamatergic synapses. These results present a distinct inhibitory mechanism for general anesthesia, whereby neuroexocytosis is selectively impaired at excitatory synapses, while inhibitory synapses remain functional. This suggests a presynaptic inhibitory mechanism that complements the other inhibitory effects of these drugs.

Exogenous Ketone Supplement Administration Abrogated Isoflurane-Anesthesia-Induced Increase in Blood Glucose Level in Female WAG/Rij Rats.

It has been demonstrated that isoflurane-induced anesthesia can increase the blood glucose level, leading to hyperglycemia and several adverse effects. The administration of a mix of ketone diester (KE) and medium-chain triglyceride (MCT) oil, named KEMCT, abolished the isoflurane-anesthesia-induced increase in blood glucose level and prolonged the recovery time from isoflurane anesthesia in a male preclinical rodent model, Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats. While most preclinical studies use exclusively male animals, our previous study on blood glucose changes in response to KEMCT administration showed that the results can be sex-dependent. Thus, in this study, we investigated female WAG/Rij rats, whether KEMCT gavage (3 g/kg/day for 7 days) can change the isoflurane (3%)-anesthesia-induced increase in blood glucose level and the recovery time from isoflurane-evoked anesthesia using the righting reflex. Moreover, KEMCT-induced ketosis may enhance both the extracellular level of adenosine and the activity of adenosine A1 receptors (A1Rs). To obtain information on the putative A1R mechanism of action, the effects of an A1R antagonist, DPCPX (1,3-dipropyl-8-cyclopentylxanthine; intraperitoneal/i.p. 0.2 mg/kg), on KEMCT-generated influences were also investigated. Our results show that KEMCT supplementation abolished the isoflurane-anesthesia-induced increase in blood glucose level, and this was abrogated by the co-administration of DPCPX. Nevertheless, KEMCT gavage did not change the recovery time from isoflurane-induced anesthesia. We can conclude that intragastric gavage of exogenous ketone supplements (EKSs), such as KEMCT, can abolish the isoflurane-anesthesia-induced increase in blood glucose level in both sexes likely through A1Rs in WAG/Rij rats, while recovery time was not affected in females, unlike in males. These results suggest that the administration of EKSs as an adjuvant therapy may be effective in mitigating metabolic side effects of isoflurane, such as hyperglycemia, in both sexes.

The immune response to systemically administered endotoxin in the murine intestinal microcirculation under pentobarbital versus isoflurane anesthesia.

Pentobarbital and isoflurane are commonly used veterinary anesthetics. Due to the dangers of overdose by repeat-bolus regimen of pentobarbital, isoflurane has been recommended. However, literature suggests isoflurane-induced inhibition of cytokine and adhesion molecule release, impacting leukocyte adhesion. This study aims to characterize the impacts of pentobarbital versus isoflurane on leukocyte interactions within the intestinal microcirculation with and without endotoxin challenge. Female BALB/c mice were subjected to pentobarbital or isoflurane (N = 20) and challenged with endotoxin or saline by intraperitoneal injection. The mice were kept under anesthesia for 2 hours. Fluorochromes, rhodamine-6 G and fluorescein isothiocyanate, were injected intravenously. To visualize leukocyte adhesion within the intestinal microcirculation, laparotomy and intravital microscopy was performed. Leukocyte rolling and adhesion was quantified offline in a blinded fashion. Within collecting venules, leukocyte rolling and adhesion showed no significant differences between pentobarbital and isoflurane anesthesia under basal conditions. Endotoxin challenge caused a similar response in both anesthetic groups. Within postcapillary venules, no statistical differences between the two anesthetics were found for adhering leukocytes under basal conditions or following endotoxin challenge either. However, leukocyte rolling after LPS-challenge was significantly decreased in postcapillary venules during isoflurane anesthesia compared to pentobarbital anesthesia. Isoflurane anesthesia showed only minor differences in the immune response to endotoxin within the intestinal microcirculation compared to pentobarbital anesthesia. Due to the superior safety profile of volatile anesthetics, immunological studies may choose isoflurane over pentobarbital as the veterinary anesthetic of choice.

Longitudinal Assessment of Outcome Measures of Diaphragm Motor Unit Connectivity As Biomarkers of Phrenic Motor Unit Degeneration and Compensation

Phrenic motor neurons (MNs) form the final link from the central nervous system (CNS) to the diaphragm muscle. Ventilatory function is modulated by the CNS via groups of muscle fibers each controlled by a single MN (motor units). Processes such as injury, aging, and neurodegeneration can result in losses of MNs, and their motor unit (MU) counterparts, but MNs and MUs have some capacity for compensation through mechanisms such as axonal sprouting and collateral sprouting to regain connectivity with denervated muscle. Motor unit number (motor unit number estimation, MUNE), MU size (single motor unit potential amplitude, SMUP), and summated muscle excitation (compound muscle action potential amplitude, CMAP) have been used clinically and preclinically for decades to track MU connectivity but efforts have largely focused on limb muscles. We aimed to apply these measures to a model of phrenic MN degeneration (intrapleural injection of cholera toxin B fragment conjugated to saporin, CTB-SAP).We hypothesized that CTB-SAP-induced phrenic motor neuron death would result in loss of diaphragm MU number and compensatory increases in MU size. Under isoflurane anesthesia, rats were bilaterally, intrapleurally injected with CTB-SAP (25 μg) to target phrenic MNs and extra CTB (25 μg) to label surviving phrenic MNs, and control rats received unconjugated CTB (25 μg) and SAP (25 μg). Diaphragm CMAP, SMUP, and MUNE were acquired bilaterally and averaged at baseline/pre-injection (n=14), as well as 7 (n=14), 14 (n=14), 21 (n=6), and 28 (n=14) days post-injection. No baseline differences between groups were found. MUNE showed a significant change for time (p<0.05), treatment (p<0.001), and interaction time x treatment (p<0.01) with ~40% reduction of MUNE in CTB-SAP rats. Average SMUP of CTB-SAP rats demonstrated a significant change with time (p<0.05) and treatment (p<0.01), but no significant interaction with ~50-60% increase in SMUP amplitude. CMAP showed no significant change. Our results show a significant ~40% loss of MUs in CTB-SAP rats, similar to previous studies on morphological MN counts. In parallel with MU loss, MUs enlarged (increased SMUP), consistent with compensatory increases of MU size likely through MU collateral sprouting. In conclusion, our findings suggest that the use of diaphragm MU electrophysiological measures can provide insights into the onset and progression of CTB-SAP-induced pathology concerning the loss of phrenic MU integrity. Hence, these biomarkers can be used to investigate mechanisms of phrenic motor neuron degeneration and compensation, and to expedite the translation of experimental findings to clinical testing. Supported by a Spinal Cord Injury and Disease Research grant. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.